Karlsson scored the go-ahead goal midway through the second period and the Ottawa Senators won their third straight game to start the season, beating the Florida Panthers 3-1 on Thursday night.
Karlsson gave Ottawa the lead 8:28 into the second period. He intercepted Shawn Matthias' cross-ice pass in the neutral zone, skated in on the left side and wristed a right-handed shot past Jose Theodore high to the stick side.
"I haven't seen too many people get from the blue line at a dead stop to the hash marks and shoot the puck in the net like that in a real long time," Senators coach Paul MacLean said. "I thought, that's what makes you a Norris Trophy winner — the ability to sometimes make something out of nothing."
The goal was Karlsson's second of the season.
"I tried to make a read and it worked," Karlsson said. "It could have gone the other way, too."
Chris Phillips also scored for Ottawa, and Craig Anderson made 25 saves. Jason Spezza added an empty-net goal with 1:16 remaining.
"It was one of those games where the momentum swung a few times. We were beating them on the shot clock but they were beating us on the boards," Anderson said.
Tomas Fleischmann scored and Theodore stopped 34 of 36 shots for Florida. The defending Southeast Division champions fell to 1-3.
"I think we have to be in desperation mode right now," defenceman Ed Jovanovski said. "We need a win and we need one badly."
Ottawa has won 11 of the last 12 meetings between the teams and is enjoying a strong start to the abbreviated regular season.
"We know how crazy the schedule is and the way it can get," Ottawa defenceman Marc Methot said. "When we have an opportunity with those two days off coming into this game, there was no excuse with regards to winning it."
Theodore stopped Guillaume Latendresse on a penalty shot with 9:11 left in the third period. Brian Campbell was called for hooking Latendresse as the Senators player skated in on goal.
Fleischmann and Phillips both scored power-play goals to leave the score tied at 1 after one period.
"We really have to bear down and give our goalie some support," Panthers coach Kevin Dineen said. "They're creating a lot of chances against us. We had some push-back in the second period and a few opportunities in the third, but we just need a more consistent effort for us to have success."
NOTES: Florida C Stephen Weiss (lower body) did not dress. ... Ottawa concludes its two-game road trip in Florida at Tampa Bay on Friday night. The Senators then have a three-game homestand (Pittsburgh, Washington, Montreal). ... Philadelphia visits Florida on Saturday night. ... The Panthers' only win in their last 12 games against Ottawa came at home on March 4, 2012.